Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
  • B62D—MOTOR VEHICLES; TRAILERS
  • B62D7/00—Steering linkage; Stub axles or their mountings
  • B62D7/20—Links, e.g. track rods
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60G—VEHICLE SUSPENSION ARRANGEMENTS
  • B60G3/00—Resilient suspensions for a single wheel
  • B60G3/18—Resilient suspensions for a single wheel with two or more pivoted arms, e.g. parallelogram
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60G—VEHICLE SUSPENSION ARRANGEMENTS
  • B60G2200/00—Indexing codes relating to suspension types
  • B60G2200/10—Independent suspensions
  • B60G2200/18—Multilink suspensions, e.g. elastokinematic arrangements
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60G—VEHICLE SUSPENSION ARRANGEMENTS
  • B60G2200/00—Indexing codes relating to suspension types
  • B60G2200/40—Indexing codes relating to the wheels in the suspensions
  • B60G2200/44—Indexing codes relating to the wheels in the suspensions steerable
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60G—VEHICLE SUSPENSION ARRANGEMENTS
  • B60G2202/00—Indexing codes relating to the type of spring, damper or actuator
  • B60G2202/40—Type of actuator
  • B60G2202/42—Electric actuator

Definitions

• the present invention relates to a device for steering vehicle wheels.
• JP-A-2007-8285 discloses a steering device in which the vehicle body and the wheel-mounting portion on one side are connected to each other by a pair of front and rear arms that can extend and contract, and the lengths of the front and rear arms are changed as appropriate to make a virtual kingpin axis variable.
• JP-A-6-255527 also discloses a technique related to the present invention.
• the present invention provides a vehicle steering device that ensures a larger steering angle than in the related art while making a virtual kingpin axis variable.
• a vehicle steering device includes left and right arm mechanisms placed between a vehicle body and respective wheel-mounting portions, and arm driving means for driving the left and right arm mechanisms independently from each other.
• Each of the left and right arm mechanisms has a front arm and a rear arm.
• One end of the front arm is rotatably connected at a wheel-side front connecting point to the wheel-mounting portion, and the other end is rotatably connected at a body-side front connecting point to the vehicle body.
• one end of the rear arm is rotatably connected at a wheel-side rear connecting point to the wheel-mounting portion, and the other end is rotatably connected at a body-side rear connecting point to the vehicle body.
• the wheel-side front connecting point and the wheel-side rear connecting point are spaced apart from each other in a longitudinal direction of a vehicle, and the body-side front connecting point and the body-side rear connecting point are spaced apart from each other in the longitudinal direction of the vehicle.
• the front arm and the rear arm each include a plurality of links. Adjacent links thereof are rotatably connected to each other at an intermediate connecting point.
• the arm driving means drives the left and right arm mechanisms such that angles of the links around the body-side front connecting point, the body-side rear connecting point, the intermediate connecting points, the wheel-side front connecting point, and the wheel-side rear connecting point are uniquely determined.
• each of the front arm and the rear arm is mounted to rotatably connect a plurality of links at the intermediate connecting point, as compared with a case where each of the front arm and the rear arm is formed by a single link, the distance between the body-side connecting point and the wheel-side connecting point can be adjusted over a larger range. This makes it possible to provide a larger steering angle than in the related art.
• the arm driving means has a number of link driving devices equal to a number obtained by subtracting 3 from a total number of the body-side front connecting point, the body-side rear connecting point, the intermediate connecting points, the wheel-side front connecting point, and the wheel-side rear connecting point in each of the left and right arm mechanisms.
• the link driving devices are respectively placed in association with a number of connecting points equal to the number of the link driving devices and selected from among the body-side front connecting point, the body-side rear connecting point, the intermediate connecting points, the wheel-side front connecting point, and the wheel-side rear connecting point.
• the link driving devices rotationally drive the links around corresponding connecting points to specify angles of the links.
• Each of the front arm and rear arm includes a minimum of two links.
• each arm mechanism forms a link mechanism having a total of six connecting points including a pair of body-side connecting points, a pair of wheel-side connecting points, and a pair of intermediate connecting points. Since the space between the wheel-side connecting points can be regarded as a single link, and the space between the body-side connecting points can be regarded as a single link fixed to the vehicle body, if the angles of links around a number of connecting points equal to the total number of connecting points minus 3 are specified, the positions of the remaining three connecting points are also uniquely determined. Thus, it is possible to make the position of a virtual kingpin axis for the wheel variable by operating the arm mechanism, while providing a required steering angle to the wheel.
• the link driving devices may each include a servomotor.
• Link angles can be easily specified by rotationally driving the links around the connecting points by the servomotors. Further, when the link angles are specified by the link driving devices, link angles around the other three connecting points are also uniquely determined, so there is no need for actively controlling the positions of those connecting points. Therefore, as a result of the angles of the links around the selected connecting points being specified by the link driving devices, angles of links around unselected connecting points with which the link driving devices are not associated may be determined. This minimizes the number of link driving devices required for operating the arm mechanism, thereby achieving reduced device size and simplified control.
• a second aspect of the present invention provides a vehicle steering device including an arm mechanism that is placed between a vehicle body and a wheel-mounting portion and has a front arm and a rear arm.
• the front arm has one end rotatably connected at a wheel-side front connecting point to the wheel-mounting portion, and the other end is rotatably connected at a body-side front connecting point to the vehicle body.
• the rear arm has one end rotatably connected at a wheel-side rear connecting point to the wheel-mounting portion, and the other end is rotatably connected at a body-side rear connecting point to the vehicle body.
• the wheel-side front connecting point and the wheel-side rear connecting point are spaced apart from each other in a longitudinal direction of a vehicle.
• the body-side front connecting point and the body-side rear connecting point are spaced apart from each other in the longitudinal direction of the vehicle and fixed in position with respect to the vehicle body.
• the front arm and the rear arm each includes a plurality of links.
• Adjacent links of the plurality of links are rotatably connected to each other at an intermediate connecting point.
• each of the front arm and rear arm has a plurality of links that are rotatably connected at the intermediate connecting point. Therefore, as compared with a case where each of the front arm and the rear arm is formed by a single link, the distance between the body-side connecting point and the wheel-side connecting point can be adjusted over a larger range. As a result, a larger steering angle can be provided to the wheel than in the related art.
• FIG. 1 is a view showing a state of a steering device according to an embodiment of the present invention when a vehicle is traveling straight ahead;
• FIG. 2 is a view showing how a left turn is executed with a virtual kingpin axis set at each of the front and rear ends of the front wheel;
• FIG. 3 is a view showing how a left turn is executed, with a virtual kingpin axis for the inside turning wheel set at the center of the front wheel and a virtual kingpin axis for the outside turning wheel set at the front end of the front wheel;
• FIG. 4 is a block diagram showing the schematic configuration of the control system of the steering device shown in FIG. 1;
• FIG. 5 is a flowchart showing a steering control routine that is executed by a steering controller shown in FIG. 4; and FIG. 6 is a view showing a specific example of the steering device shown in FIG. 1.
• FIG. 1 shows a state of a steering device according to an embodiment of the present invention when a vehicle is traveling straight ahead.
• suffixes L and R are provided to reference numerals indicating individual components to differentiate between the left and right. However, these suffixes may sometimes be omitted in the following description when there is no need to differentiate between the left and right.
• a steering device 1 in FIG. 1 steers left and right front wheels 2L, 2R of a passenger vehicle.
• the front wheels 2L, 2R are mounted to wheel-mounting portions 3L, 3R, respectively.
• the wheel-mounting portions 3L, 3R are assembly parts including spindles 4L, 4R serving as the centers of rotation of the front wheels 2L, 2R.
• the front mounting portion 3 may be an in-wheel motor, in which case the output shaft of the in-wheel motor is the spindle 4.
• the steering device 1 includes left and right arm mechanisms 5L, 5R that are respectively provided in correspondence to the left and right wheel-mounting portions 3.
• the arm mechanisms 5L, 5R are symmetrical about the longitudinal centerline CL of the vehicle.
• the left arm mechanism 5L has a pair of arms, a front arm 7L and a rear arm 8L, which are arranged in the longitudinal direction (vertical direction in FIG. 1) of the vehicle.
• the front arm 7L includes an inner link 1OL and an outer link HL. One ends of the respective links are rotatably connected to each other at an intermediate connecting point Mf.
• the rear arm 8L includes an inner link 12L and an outer link 13 L. One ends of the respective links are rotatably connected to each other at an intermediate connecting point Mr.
• the other ends of the inner links 1OL, 12L are rotatably connected to an arm-mounting portion 14, which forms a part of the vehicle body, at body-side connecting points Bf, Br, respectively.
• the body-side connecting points Bf, Br are spaced apart from each other in the longitudinal direction, and their positions are fixed with respect to the vehicle body.
• the other ends of the outer links HL, 13L are rotatably connected to the wheel-mounting portion 3L at wheel-side connecting points Wf, Wr, respectively.
• the wheel-side connecting points Wf, Wr are spaced apart from each other in the longitudinal direction.
• the front arm 7L and the rear arm 8L have a plurality of links 1OL, HL and 12L, 13L that are connected in series from the body-side connecting points Bf, Br to the wheel-side connecting points Wf, Wr via the intermediate connecting points Mf, Mr, respectively.
• the front arm 7L and the rear arm 8L are longitudinally symmetrical about an axle centerline AX.
• the axle centerline AX is a line along the vehicle width direction connecting between the spindles 4L, 4R when the front wheels 2L, 2R are pointing straight ahead.
• the links 1OL, HL, 12L, 13L has a fixed length.
• the right arm mechanism 5R has a pair of arms, a front arm 7R and a rear arm 8R, which are arranged in the longitudinal direction of the vehicle.
• the front arm 7R includes an inner link 1OR and an outer link HR. One ends of the respective links are rotatably connected to each other at an intermediate connecting point Mf.
• the rear arm 8R includes an inner link 12R and an outer link 13R. One ends of the respective links are rotatably connected to each other at an intermediate connecting point Mr.
• the other ends of the inner links 1OR, 12R are rotatably connected to the arm-mounting portion 14 at body-side connecting points Bf, Br, respectively.
• the body-side connecting points Bf, Br are spaced apart from each other in the longitudinal direction, and their positions are fixed with respect to the vehicle body.
• the other ends of the outer links HR, 13R are rotatably connected to the wheel-mounting portion 3R at wheel-side connecting points Wf, Wr, respectively.
• the wheel-side connecting points Wf, Wr are spaced apart from each other in the longitudinal direction. That is, the front arm 7R and the rear arm 8R have a plurality of links 1OR, HR and 12R, 13R that are connected in series from the body-side connecting points Bf, Br to the wheel-side connecting points Wf, Wr via the intermediate connecting points Mf, Mr, respectively.
• the front arm 7R and the rear arm 8R are longitudinally symmetrical about the axle centerline AX: In this embodiment, the links 1OR, HR, 12R, 13R has a fixed length.
• each arm mechanism 5 is a 6-joint link mechanism that connects six link elements, that is, the wheel-mounting portion 3, the links 10 to 13, and the arm-mounting portion 14,rotatably to each other at six connecting points Bf, Mf, Wf, Wr, Mr, Br.
• the steering device 1 is provided with an arm driving device 20 as arm driving means for driving the arm mechanisms 5L, 5R independently from each other.
• the arm driving device 20 has a first servomotor 21, a second servomotor 22, and a third servomotor 23 that are provided for each arm mechanism 5, as link driving devices for rotationally driving the links 10, 12, 13 to specify their angles.
• the first servomotor 21 rotationally drives the inner link 10 around the connecting point Bf with respect to the arm-mounting portion 14, and the second servomotor 22 rotationally drives the inner link 12 around the connecting point Br with respect to the arm-mounting portion 14.
• the third servomotor 23 rotationally drives the outer link 13 around the connecting point Mr with respect to the inner link 12 of the rear arm 8.
• each arm mechanism 5 by adjusting the angles of the links 10, 12, 13 by the servomotors 21 to 23, a virtual kingpin axis Kp of the front wheel 2 and the inclination (steering angle) of the wheel-mounting portion 3 with respect to the longitudinal centerline CL are uniquely determined.
• FIG. 2 shows an example of the state of the steering device 1 during a left turn.
• the left front wheel 2L is steered around the virtual kingpin axis KpL that is set at its rear end and on the centerline AL
• the right front wheel 2R is steered around the virtual kingpin axis KpR that is set at its front end and on the centerline AR.
• the operations of the servomotors 21 to 23 when steering the vehicle from the straight-ahead state in FIG. 1 to the state in FIG. 2 are as follows.
• the first servomotor 21L is driven so as to rotate the link 1OL counterclockwise around the connecting point Bf
• the second servomotor 22L is driven so as to rotate the link 12L clockwise around the connecting point Br
• the third servomotor 23L is driven so as to rotate the link 13L counterclockwise to an extent that makes the length of the front arm 7L (the distance between the connecting points Bf, Wf) substantially maximum.
• the first servomotor 21R is driven so as to rotate the link 1OR clockwise around the connecting point Bf
• the second servomotor 22R is driven so as to rotate the link 12R counterclockwise around the connecting point Br
• the third servomotor 23R is driven so as to rotate the link 13R clockwise to an extent that makes the length of the rear arm 8R (the distance between the connecting points Br, Wr) substantially maximum.
• FIG. 2 shows one illustrative example of steering of the front wheel 2.
• the virtual kingpin axis Kp can be set not only at the front or rear end of the front wheel 2 but at an arbitrary position, by driving the servomotors 21 to 23 of each arm mechanism 5 as appropriate.
• FIG. 3 as for the left front wheel 2L that becomes the inside turning wheel, it is possible to set the virtual kingpin axis KpL at the center of its ground-contacting surface and steer the front wheel 2L around this virtual kingpin axis KpL.
• the virtual kingpin axis Kp can be set at an optimum position in accordance with the vehicle's loading condition, longitudinal weight distribution, vehicle speed, road condition, and the like.
• a conceivable way of setting the virtual kingpin axis Kp is to set the virtual kingpin axis Kp in the manner as illustrated in FIG. 2 when a large steering angle is required, for example.
• the steering torque of the front wheel 2 can be minimized by setting the virtual kingpin axis Kp at substantially the center of the ground-contacting surface of the front wheel 2, like the left front wheel 2Lin FIG. 3.
• the left and right arm mechanisms 5L, 5R can be driven independently from each other. It is thus also possible to adjust the Ackerman rate.
• the Ackerman rate refers to the ratio between the left and right steering angles in a turn.
• the steering device 1 also makes it possible to change the tread between the front wheels 2L, 2R. That is, by driving the servomotors 21 to 23 in such a way that the wheel-side connecting points Wf, Wr are displaced equally in the direction along the axle centerline AX 5 the tread can be increased as indicated by the imaginary line (chain double-dashed line) in FIG. 1, or the increased tread can be reduced again, without changing the steering angle of the front wheel 2.
• This makes it possible to realize changes in tread according to the drive condition, such as by setting the thread small during traveling on an ordinary road or in an urban area, or increasing the thread during traveling on an expressway to enhance the stability of the vehicle.
• the connecting structure may be so determined as to allow the arms 7, 8 to rotate around the vertical axis of the vehicle. It should be noted, however, that by connecting the links via bushes, spherical bearings, or the like, the arms 7, 8 may be allowed to rotate somewhat around the horizontal axis as well with respect to the wheel-mounting portion 3 or the arm-mounting portion 14. Vertical movement of the front wheels 2L, 2R with respect to the vehicle body may be permitted by making the arms 7, 8 vertically displaceable with respect to the wheel-mounting portion 3 or the arm-mounting portion 14.
• a spring or damper may be provided between the vehicle body and the arms 7, 8 to allow the arm mechanism 5 to function as a suspension.
• the front wheel 2 may be supported by a suspension mechanism provided separately from the steering device 1 so that the steering device 1 is responsible only for the steering drive of the front wheel 2.
• FIG. 4 is a block diagram of the control system.
• the control system of the steering device 1 includes a steering controller (hereinafter, abbreviated as "controller") 30 that is steering control means for controlling the actions of the servomotors 21 to 23 in conjunction with operation of the steering member.
• the controller 30 is configured as a computer unit.
• the controller 30 is connected with the above-described left and right servomotors 21 to 23 as its control targets.
• the controller 30 is connected with a state detecting device 31 that detects various states that are to be referred to in the control of the servomotors 21 to 23.
• the state detecting device 31 includes a steering angle sensor 32 that detects an operation angle (steering operation angle) of the steering member from the neutral position (position when traveling straight ahead).
• the term steering operation angle as used herein includes information that makes it possible to identify the operation direction of the steering member from the neutral position.
• the state detecting device 31 may also include various sensors such as a vehicle speed sensor 33 and a yaw rate sensor 34 which detect parameters indicating the vehicle's motion state (hereinafter, referred to as vehicle motion parameters).
• a body slip angle, lateral G-force, or the like may be also selected as appropriate, other than the vehicle speed or yaw rate.
• the state detecting device 31 may include a sensor that detects the axial loads on the front and rear wheels of the vehicle, or a sensor that detects the road surface state.
• the state detecting device 31 may include not only sensors but also, for example, input means for inputs from the driver of the vehicle.
• FIG. 5 is a flowchart showing a steering control routine that is executed by the controller 30 to steer the front wheel 2.
• this routine first, it is determined in step SIl whether or not the steering member has been operated, on the basis of an output signal from the steering angle sensor 24. If no steering operation has been made, the process is suspended, and the process proceeds to the next step S12 if a steering operation is made.
• step S 12 the state in which the vehicle is placed is detected by referring to an output from the state detecting device 31.
• the positions of the virtual kingpin axes KpL, KpR corresponding to the detected state are determined.
• step S 13 can be realized by classifying states that are detected by the state detecting device 31 into several types, calculating the optimum virtual kingpin axes Kp for individual types in advance by computer simulation or the like and creating table data of these correspondences, and storing the table data into the ROM of the controller 30.
• step S13 After the position of the virtual kingpin axis Kp is determined in step S13, a steering operation angle of the steering member is detected in step S14.
• step S 15 that follows, steering angles for the respective front wheels 2L, 2R according to the steering operation angle are determined.
• step S 16 drive amounts for the respective servomotors 21 to 23 are determined on the basis of the position of the virtual kingpin axis Kp and the steering angles.
• the servomotors 21 to 23 are driven in accordance with the determined drive amounts in step S 17. Thereafter, the process is returned to step SIl, and the same procedure is repeated subsequently.
• the steering angles of the front wheels 2L, 2R are controlled while controlling the position of the virtual kingpin axis Kp in accordance with operation of the steering member.
• the driver may be made to select a drive mode, and the servomotors 21 to 23 may be controlled in such a way that the optimum tread is set in accordance with the selection result.
• FIG. 6 shows only the left arm mechanism 5L, and the right arm mechanism 5R is symmetrical to the left arm mechanism 5L.
• the link 12L of the rear arm 8L is formed as a member that is bent in an L shape.
• the line segment connecting between the body-side connecting point Br and the intermediate connecting point Mr corresponds to the link 12Lin FIG. 1.
• the present invention is not limited to the above-described embodiment but may be implemented in various embodiments.
• the servomotors 21 to 23 may be placed at the wheel-side connecting points Wf, Wr and another connecting point. That is, it suffices that the servomotors 21 to 23 be placed in association with three connecting points out of the six connecting points.
• a configuration is possible in which each of the front arm 7 and the rear arm 8 includes three or more links, the links are connected in series, and the links are rotatably connected to each other at the connecting point (intermediate connecting point) between adjacent links.
• the link angles around a number of connecting points equal to the total number of connecting points minus 3 are specified by the link driving devices, then the link angles around the three other remaining connecting points are uniquely determined.
• a link driving device at at least one of the three remaining connecting points, and control the actions of individual link driving devices in such a way as to ensure that there will be no inconsistency in link angle between this link driving device and the link driving devices at other connecting points.
• the link driving device to be used is not limited to a servomotor, but various types of actuator or driving mechanism that can rotationally drive a link around a connecting point to specify its angle may be used.
• a link driving device of a type which transmits the rotary motion of one of the servomotors to another connecting point by a motion transmission mechanism such as a gear mechanism to thereby change the link angle around this connecting point.
• a motion transmission mechanism such as a gear mechanism to thereby change the link angle around this connecting point.
• at least one of the links may be a direct drive actuator that can extend and contract.
• Plural sets of the above-mentioned steering device may be provided in the vertical direction of the vehicle, and the arm mechanisms may be driven independently from each other in individual sets.
• the positions of the wheel-side connecting points Wf, Wr in individual sets can be set independently from each other, so the virtual kingpin axis can be operated three-dimensionally to change the camber angle, the caster angle, and the toe angle.
• spherical bearings, bushes, or the like are used for individual connecting points so that links are connected in a manner allowing their relative rotation in the three-dimensional direction around the connecting points.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Transportation (AREA)
• Steering-Linkage Mechanisms And Four-Wheel Steering (AREA)
• Vehicle Body Suspensions (AREA)
• Power Steering Mechanism (AREA)
• Steering Control In Accordance With Driving Conditions (AREA)
• Superstructure Of Vehicle (AREA)

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Family Cites Families (32)

• 2007
  • 2007-11-22 JP JP2007302370A patent/JP4389993B2/ja active Active
• 2008
  • 2008-11-21 CN CN2008801174982A patent/CN101873961B/zh not_active Expired - Fee Related
  • 2008-11-21 WO PCT/IB2008/003163 patent/WO2009066160A1/en active Application Filing
  • 2008-11-21 US US12/674,098 patent/US8256780B2/en active Active
  • 2008-11-21 DE DE112008003171.1T patent/DE112008003171B4/de active Active

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